We have had an extension built as a shell only and it is getting close to the plasterboard stage.
We want the ceiling to be 300mm lower than the roof joists which are spaced at 450mm between centres. The area is roughly 5m long by 1.5m wide.
My plan is to bolt a length of 3x2" along each length then use joist hangers to fit 3x2" cross pieces.
Does this sound like the best way to go about things? If so should I stick with 450mm centres or go for 400mm centres? Also how much should I allow for the finished thickness of the plastered ceiling - plasterboard + skim?
Sean